The present invention relates to a method and apparatus for reducing the amount of gas consumed during welding operations. More particularly, the invention relates to preventing gas-surge in M.I.G. and T.I.G. welding systems and improving the arc starting characteristics of welding equipment.
A typical gas delivery system conducts compressed gas from a high-pressure cylinder, through a hose, to a welding machine. The rate at which gas flows through the system is affected by the relationship between a flowmeter, often connected directly to a cylinder or a manifold system and a valve switch at the welding apparatus in use, often comprised of a solenoid. To maintain availability of gas throughout the system, the regulator used will reduce the pressure available at the solenoid, however, pressure will still be greater than needed for actual welding to ensure that there is a regular gas flow. In addition the hoses used to transport gas are often flexible and will expand when held under pressure increasing the volume and pressure of gas between the flowmeter and the solenoid. The higher static pressure is discharged on initial releases of gas for use. This discharge creates a short term gas-surge or large flow of gas due to the build up of the high static pressure within the line. The amount of gas exhausted is far greater than the amount needed under transient welding conditions and is disruptive to the welding process.
Gas-surge wastes valuable inert welding gas. Welding operations cannot begin until the gas-surge has passed and gas-flow rate has normalized. The amount of actual surge is affected by variables such as the condition of the rubber hose, the hose length, and the ambient air temperature. Whatever the amount, gas surge is a persistent problem in the welding industry wasting time and money.
Prior art devices which have addressed this problem have failed to provide a satisfactory solution. U.S. Pat. No. 4,341,237 to Stauffer teaches an apparatus for reducing the waste of welding gas by temporarily storing gas in a surge tank and thereafter dispensing gas at a uniform rate. The limitations of this device are readily apparent. The device is bulky, consumes a significant amount space, is heavy, and not substantially portable. The Stauffer device also has a plurality of moving parts which are subject to breakage, and are expensive to assemble and repair.
Other known prior art consists of variable restrictions in the form of sliding occlusions that create a variable size barrier to glass flow at the welding apparatus. In their simplest form, these systems are essentially adjustable valves that gate off gas flow. A problem with these systems is that the adjustable valve and gate orifices are not of a uniform shape and size, often with hard angular edges causing turbulence in the gas flow. These types of adjustable valve and gate systems are also expensive, cumbersome and prone to blockage or failure. Another defect of the valve and gate flow limitation systems is that the exact flow rate created is difficult to gauge and often unknown and must be reset and adjusted on a regular basis.
The present invention solves the problems of gas-surge while avoiding the shortcomings inherent in prior art devices. A preferred embodiment of the present invention consists of a series of removable orifice bodies with a gas-flow passage which is inserted into a valve body which has two ends. One end of the valve body containing the orifice body is connected to the gas inlet side of the solenoid of a welding unit. The hose used to transport gas to the solenoid is then attached to the second end of the valve body. The gas-flow channel of the orifice body restricts the maximum rate at which gas can flow from the hose into the solenoid. Gas-flow may be set to any level below the maximum threshold by adjusting the flowmeter; just as in normal welding operations. But gas-flow through the solenoid cannot exceed the maximum rate permitted by the particular diameter of the gas-flow passage of the orifice body.
The benefit of the invention is that maximum gas-flow rate may be adjusted up or down by substituting one of a plurality of interchangeable orifice bodies. Each orifice body may be removably inserted into the valve body and each orifice body contains a specific gas-flow passage of a specific size. To allow flow at a higher rate, an orifice body with a larger diameter gas-flow passage is installed. When conditions call for a lower flow rate, an orifice body with a smaller gas-flow passage is used. The use of precision set diameter chamfered nozzles for the gas entering and exiting the gas-flow passage permits gas to flow at a steady rate without excessive turbulence. The use of the invention also provides an inexpensive device and method for variably setting a known maximum gas flow rate to a solenoid in a welding apparatus.